CN110121453B

CN110121453B - System and method for controlling vehicle

Info

Publication number: CN110121453B
Application number: CN201780081786.6A
Authority: CN
Inventors: J·J·沃尔夫; T·布朗恩; H·杨; L·肖特; E·T·佩特拉克; R·费舍尔; J·查德维尔; M·瓦格纳; C·巴列霍; S·西莱森; L·本奇; K·P·内德利; A·K·库马
Original assignee: Transportation IP Holdings LLC
Current assignee: Transportation IP Holdings LLC
Priority date: 2016-11-01
Filing date: 2017-11-01
Publication date: 2022-09-02
Anticipated expiration: 2037-11-01
Also published as: EP3519266A4; CN110121453A; WO2018085324A1; EP3519266A1; JP2019536403A; AU2017353698B2; JP2023040053A; AU2017353698A1; CN115384505A; JP7212233B2

Abstract

A vehicle control system determines a non-zero upper limit for deceleration of a vehicle to prevent the vehicle from rolling back along a grade on which the vehicle is currently traveling upward. Determining, by a controller, a non-zero upper limit for the deceleration based on a load carried by the vehicle, a speed of the vehicle, and a grade of a current driving route of the vehicle. A controller is configured to monitor the deceleration of the vehicle and automatically prevent the deceleration of the vehicle from exceeding a non-zero upper limit by controlling brakes and/or motors of the vehicle. The controller is further configured to activate a brake and/or supply current to a motor of the vehicle when the vehicle is moving up a grade at a non-zero speed to prevent the vehicle from rolling backwards.

Description

System and method for controlling vehicle

Cross Reference to Related Applications

This application claims priority from U.S. provisional patent application No.62/480,590 filed on 3/4/2017. This application also claims priority from U.S. provisional patent application No.62/415,589 filed on 1/11/2016.

Technical Field

Embodiments of the inventive subject matter described herein relate to vehicle control. Other embodiments relate to controlling a vehicle to prevent rollback.

Background

Vehicles such as off-highway mining vehicles "OHV" and load-haul-unload vehicles "LHD" for mining and carrying heavy loads from underground mines are well known. LHDs and other vehicles are generally available in both diesel and electric versions, and often use electric wheels to propel or decelerate the vehicle in an energy efficient manner. This efficiency is typically achieved by using a high horsepower diesel engine in combination with an alternator, a main traction inverter, and a wheel drive assembly mounted within the tires of the vehicle. The diesel engine is directly associated with the alternator such that the diesel engine drives the alternator. The alternator provides electrical power to a main traction inverter that provides electrical energy at a controlled voltage and frequency to an electric drive motor of the wheel drive assembly. Each wheel drive assembly is fitted with a planetary gear transmission that converts the rotational energy of the associated drive motor to a high torque, low speed rotational energy output that is provided to the wheels of the vehicle.

In addition to powering the main traction inverter to power the electric drive motor to propel the vehicle, the alternator also powers hydraulic pumps and hydraulic motors used by various auxiliary vehicle systems, such as for jounce movement (bucket movement) and for the application of service and parking brakes.

Operating these vehicles on grade (grade) may present challenges, particularly for inexperienced operators, due to the weight of the vehicles, the loads carried, and the environment in which the vehicles are used. Accordingly, it may be desirable to provide a system and method for controlling a vehicle that differs from existing systems and methods.

Disclosure of Invention

In one embodiment, a method for controlling a vehicle is provided. The method comprises the following steps: controlling at least one traction motor of the vehicle to provide controlled deceleration of the vehicle when traveling on a grade in the selected direction of travel and automatically applying service brakes of the vehicle when the vehicle is moving in the selected direction of travel.

In another embodiment, a system is provided. The system comprises: a control unit configured to be electrically connected to a drive system of a vehicle, the drive system comprising at least one traction motor for providing motive power to the vehicle; and a service brake associated with at least one wheel of the vehicle. In the absence of a command to provide motive force in the selected direction of travel, the control unit is configured to automatically apply the service brakes to prevent the vehicle from rolling backwards when the vehicle is moving in the selected direction of travel.

In one embodiment, a method for controlling a vehicle is provided. The method comprises the following steps: the method includes determining a selected direction of travel of the vehicle, monitoring a direction of operation of a motor of the vehicle, monitoring a speed of the motor, and automatically applying a service brake of the vehicle to prevent the vehicle from rolling backwards when a rollback condition is detected.

In another embodiment, a system is provided. The system comprises: a control unit configured to be electrically connected to a drive system of a vehicle, the drive system including at least one traction motor for providing motive power to the vehicle; and a service brake associated with at least one wheel of the vehicle. The control unit is configured to automatically apply the service brakes to prevent the vehicle from rolling backwards when a rollback state is detected.

In yet another embodiment, a vehicle is provided. The vehicle includes a drive system including a traction motor drivingly connected to wheels of the vehicle, the motor configured to provide motive force to propel the vehicle in a selected direction of travel in a propulsion mode of operation; a controller electrically connected to the drive system; and a friction brake associated with at least one wheel of the vehicle. The controller is configured to automatically engage the friction brake to prevent the vehicle from rolling backwards when a rollback condition is detected.

In an embodiment, a control system control (e.g., a braking control system) for a vehicle includes an electric drive system associated with at least a first set of wheels of the vehicle, and a drive system control unit configured to control the electric drive system to selectively provide electric motive power to the at least first set of wheels to propel the vehicle and electrically decelerate to slow the vehicle. The system further comprises: a friction braking system associated with at least one of the first or second set of wheels of the vehicle; and a friction brake control unit configured to control the friction braking system for applying friction braking to at least one of the first set of wheels or the second set of wheels. The drive system control unit is further configured to communicate with the friction brake control unit to control the amount of friction brake application during vehicle stopping and starting. For example, the drive system control unit may be configured to communicate with the friction brake control unit to at least partially automatically control the amount of friction brake application during stopping and starting of the vehicle on an incline grade on which it is located.

In another embodiment, a method of controlling a vehicle includes, at a drive system control unit of the vehicle, controlling an electric drive system associated with at least a first set of wheels of the vehicle to selectively provide electrical motive power to the at least first set of wheels to propel the vehicle and electrically decelerate to slow the vehicle. The method also includes determining a torque level required for the vehicle to move from stopped to moving up an inclined grade, and in response to an input from an operator control for moving the vehicle up the grade, communicating with a friction brake control unit of the vehicle to remove a friction brake application that holds the vehicle stopped, and simultaneously controlling an electric drive system of the vehicle to provide electric motive force for moving the vehicle from stopped to moving up the grade without significant vehicle rollback according to the determined torque level.

In another embodiment, a method of controlling a vehicle includes, at a drive system control unit of the vehicle, controlling an electric drive system associated with at least a first set of wheels of the vehicle to selectively provide electrical motive power to the at least first set of wheels to propel the vehicle and electrically decelerate to slow the vehicle. The method also includes determining a force required to hold the vehicle on an incline grade on which the vehicle is located, and communicating with a friction brake control unit of the vehicle to reduce or increase an amount of friction brake application applied to at least one of the first set of wheels or the second set of wheels of the vehicle in accordance with the determined force to hold the vehicle on the incline grade.

In one embodiment, a vehicle control system includes a controller configured to determine a non-zero upper limit for vehicle deceleration. The controller is configured to determine a non-zero upper limit to prevent the vehicle from rolling back along a grade on which the vehicle is currently traveling upward. A non-zero upper limit for deceleration is determined by the controller based on a load carried by the vehicle, a speed of the vehicle, and a grade of a current travel path of the vehicle. The controller is configured to monitor deceleration of the vehicle and automatically prevent the deceleration of the vehicle from exceeding a non-zero upper limit by controlling brakes and/or motors of the vehicle. The controller is further configured to activate the brake and/or supply current to a motor of the vehicle to prevent the vehicle from rolling backwards when the vehicle is currently moving up a grade at a non-zero speed.

In one embodiment, the method includes determining a non-zero upper limit for deceleration of the vehicle to prevent the vehicle from rolling back along a grade on which the vehicle is currently traveling upward. A non-zero upper limit for deceleration is determined based on the load carried by the vehicle, the speed of the vehicle, and the grade of the current path traveled by the vehicle. The method includes monitoring deceleration of the vehicle and automatically preventing the deceleration of the vehicle from exceeding a non-zero upper limit by controlling brakes and/or motors of the vehicle. Deceleration of the vehicle is prevented from exceeding a non-zero upper limit by activating a brake and/or supplying current to a motor of the vehicle when the vehicle is moving up a grade at a non-zero speed to prevent the vehicle from rolling backwards.

In one embodiment, a vehicle control system includes a controller configured to determine a selected direction of travel of a vehicle, a direction of operation of a motor of the vehicle, and a speed of operation of the motor. The controller is configured to identify a rollback state of the vehicle in response to an operating direction of a motor of the vehicle being different from a selected direction of travel of the vehicle. The controller is further configured to automatically slow or stop movement of the vehicle by automatically activating a brake of the vehicle in response to the rollback state being identified and the operating speed of the motor exceeding a specified non-zero speed threshold.

In one embodiment, a vehicle control system includes a controller configured to determine a lower limit for vehicle speed. The controller is configured to determine a lower limit to prevent the vehicle from rolling back along a grade on which the vehicle is currently traveling upward. The lower limit is determined by the controller based on the load carried by the vehicle and the grade of the route currently being traveled by the vehicle. The controller is configured to monitor the speed of the vehicle and automatically prevent the vehicle speed from falling below a lower limit by activating the brakes of the vehicle. The controller is configured to activate the brake based on a speed of the vehicle and independent of an acceleration of the vehicle. The controller is further configured to activate a brake of the vehicle to prevent the vehicle from rolling backwards when the vehicle is moving up the grade at a non-zero speed.

In one embodiment, a method comprises: the method includes receiving a throttle command indicative of an operator request to increase a throttle setting of the vehicle while engaging brakes of the vehicle, increasing torque generated by one or more motors of the vehicle in response to receiving the throttle command, and releasing the brakes of the vehicle in response to one or more of the torque generated by the one or more motors reaching a maximum available torque, the torque generated by the one or more motors reaching a target release acceleration, or a predetermined non-zero duration expiration.

In one embodiment, a method includes determining whether brakes of a vehicle have been released while the vehicle is at a standstill on a grade of a route, in response to determining that the brakes have been released, allowing the vehicle to roll backward on the grade no greater than a specified non-zero threshold distance and/or rapidly accelerating the vehicle using torque generated by one or more motors of the vehicle, and smoothly transitioning the vehicle to upward grade movement by adjusting torque generated by the one or more motors after allowing the vehicle to roll backward on the grade and/or rapidly accelerating the vehicle.

In one embodiment, a method includes repeatedly determining whether an operator input to release one or more brakes is received during a blanking interval (while one or more brakes of a vehicle in a stationary position on a grade are engaged), releasing one or more brakes of the vehicle in response to not receiving the operator input to release the one or more brakes during the blanking interval, and automatically generating torque using one or more motors of the vehicle to propel the vehicle upward along the grade.

Drawings

Referring now briefly to the drawings, wherein:

fig. 1 is a side view of a load-transport-unload vehicle equipped with a system for preventing the vehicle from rolling backwards according to an embodiment of the inventive subject matter;

FIG. 2 is a perspective view of another vehicle equipped with a system for preventing vehicle rollback according to an embodiment of the present subject matter;

FIG. 3 is a schematic view of a drive system and system for preventing a vehicle from rolling backwards according to an embodiment of the present subject matter;

FIG. 4 is a diagram illustrating a control routine for preventing a vehicle from rolling backwards according to one embodiment of the present subject matter;

fig. 5 is a diagram showing a control routine for preventing a vehicle from rolling backwards according to another embodiment of the present subject matter;

fig. 6 is a diagram showing a control routine for preventing a vehicle from rolling backwards according to another embodiment of the present subject matter;

fig. 7 is a diagram showing a control routine for preventing a vehicle from rolling back according to another embodiment of the present subject matter;

fig. 8 is a diagram showing a control routine for preventing a vehicle from rolling back according to still another embodiment of the present subject matter;

FIG. 9 is a diagram illustrating a control routine for preventing a vehicle from rolling backwards according to one embodiment of the present subject matter;

FIG. 10 is a graph illustrating operation of a system for preventing vehicle rollback according to an embodiment of the present subject matter;

FIG. 11 is a schematic diagram of an electric drive and reduction system according to an embodiment;

FIG. 12 is a block diagram illustrating a control system including a hydraulic friction brake and an electric retarder according to an embodiment;

FIG. 13 illustrates a flow chart of an embodiment of a method for controlling movement of a vehicle from a stopped position on a grade; and

FIG. 14 illustrates a flow chart of an embodiment of a method for automatically controlling movement of a vehicle on a grade when no input is provided by an operator of the vehicle.

Detailed Description

Reference will now be made in detail to exemplary embodiments of the present subject matter, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Although exemplary embodiments of the present subject matter have been described with reference to a load-transport-unload vehicle having a diesel engine for use in the underground mining industry, embodiments of the present subject matter are also generally applicable for use with internal combustion engines and vehicles using such engines. For example, the vehicle may be an off-highway vehicle designed to perform operations associated with a particular industry, such as mining, construction, farming, etc., and may include haul trucks, cranes, dozers, mining machines, farming equipment, tractors, material handling equipment, earthmoving equipment, etc. Alternatively or additionally, the vehicle may be a road vehicle, such as a tractor trailer, a road dump truck, or the like. Moreover, other embodiments of the inventive subject matter are applicable to electric-only vehicles and mechanical devices, such as battery-powered vehicles. As used herein, "electrical communication" or "electrical connection" means that certain components are configured to communicate with each other through direct or indirect signaling via direct or indirect electrical connection. As also used herein, "zero speed" refers to a condition when the vehicle is stopped/stationary. A "near zero" speed indicates a very close approach to stopping (e.g., no more than 5mph/8kph of travel in one embodiment, or no more than 1mph/1.6kph of travel in another embodiment).

Embodiments of the inventive subject matter relate to a control system (and related method) for controlling a vehicle that prevents the vehicle from rolling back on a grade. "grade" refers to a non-horizontal plane having an inclination greater or less than zero degrees. "service braking" refers to mechanical friction braking, for example, typically of the type in which brake pads are driven by an air/pneumatic or hydraulic system to engage a rotor or disc connected to a wheel or axle, and are typically separate from the propulsion system.

Fig. 1 illustrates a load-transport-unload vehicle 10 that may incorporate the control system of the present subject matter. The LHD vehicle includes a front chassis 12 connected to a rear chassis 14 by an articulated joint 16. The vehicle 10 also includes a bucket 18 at a front portion thereof for propelling overburden and/or for moving overburden and/or mined material. The bucket 118 is operable by a hydraulic lift assembly (not shown). The rear portion of the vehicle 10 is provided with a cabin 20 in which a diesel engine (in the case of a diesel engine-driven vehicle) or a battery (in the case of an electric vehicle) for supplying power to the vehicle 10 and accessories thereof are housed.

Referring to fig. 2, the vehicle may be a haul truck 30. Haul truck 30 is a dump truck specifically designed for use in high volume mining and heavy construction environments. The drive system of the haul truck includes drive wheels 32 connected to a diesel-electric power/traction system that provides motive power to the haul truck. (haul trucks and underground mining vehicles are general examples of vehicles, although in embodiments, the systems and/or methods of the inventive subject matter are embodied on haul trucks or underground mining vehicles.)

Fig. 3 schematically illustrates an example of a drive system 100 for an electric drive machine such as the LHD vehicle 10 or haul truck 30. The drive system 100 includes a primary power source such as an engine 102 (e.g., diesel engine, gasoline engine, multi-fuel engine, etc.) and a traction alternator/generator 104 mechanically connected to the engine 102 and driven by the engine 102. As shown in fig. 3, the traction alternator 104 is electrically connected to a traction bus 106. The alternator 104 is configured to provide AC power to one or more rectifiers 108 that are electrically connected to one or more power converters, e.g., first and

second inverters

110, 112, via the traction bus 106. The

inverters

110, 112 are connected to one or more motors, such as a first traction motor 114 and a second traction motor 116 associated with a first wheel and a second wheel, respectively, of a vehicle, such as the rear wheels of the vehicle 10 (including a first rear wheel 118 and a second rear wheel 120). Alternatively, the vehicle may have a single motor or more than two motors. Although two inverters and two motors are shown in fig. 3, one or more embodiments of the inventive subject matter described herein may be used with a single inverter and a single motor or more than two inverters and more than two motors on a vehicle. The rectifier 108 is configured to convert AC power received from the alternator 104 to a DC output, which is then supplied to the

inverters

110, 112 via the traction bus 106. The

inverters

110, 112 are configured to provide three-phase, variable frequency AC power to first and

second traction motors

114, 116 associated with first and second wheels 118, 120 (typically rear wheels of the vehicle) of the vehicle 10.

As also shown in fig. 3, in an embodiment, a starter motor 122 may be associated with the engine 102 for rotating the engine 102 to begin operation, as is known in the art. Additionally, the vehicle may include a battery 124, such as a 24V battery, electrically connected to the alternator 104 through a third winding 126 and a field winding 128. The battery 124 is configured to act as an alternator field static exciter to initiate operation of the electric drive system 100 of the vehicle 10.

The

traction motors

114, 116 provide traction power to move the vehicle, and may be AC or DC electric motors. When a DC traction motor is used, the output of the alternator is typically rectified to provide the appropriate DC power. When AC traction motors are used, the alternator output is typically rectified to DC and thereafter inverted to three-phase AC before being provided to the

traction motors

114, 116. During the propulsion mode of operation, power may be transferred from the engine 102 to the

traction motors

114, 116, and thus to the

wheels

118, 120 of the vehicle 10 to effect movement.

In addition to providing motive power, the

traction motors

114, 116 may also provide a braking force or force for controlling the speed of the vehicle 10 in which the drive system 100 is deployed. This is commonly referred to as dynamic braking. During a dynamic braking mode of operation, such as when movement of the vehicle is retarded, electrical power may be generated by mechanical rotation of the drive wheels and directed to the deceleration grid 130. In particular, the kinetic energy of the vehicle 10 may be converted into rotational power at the

drive wheels

118, 120. The rotation of the drive wheels may also rotate the

motors

114, 116 to generate electrical power, for example, in the form of AC power. The

inverters

110, 112 may function as a bridge (bridge) to convert the power provided by the

motors

114, 116 to DC power. The loss of DC power generated by the

motors

114, 116 may generate counter-rotating torque at the

drive wheels

118, 120 to slow the vehicle 10. Such losses may be accomplished by passing the generated current provided by the

inverters

110, 112 through a resistor, such as the dynamic braking grid 130 or the retarding grid, as shown.

As further shown in FIG. 3, the drive system 100 also includes an engine radiator fan 132 driven by the engine 102 to provide cooling to the engine 102. The system 100 may also include one or more control and motor cooling fans 134 mechanically coupled to the alternator 104. The cooling fan 134 is configured to provide cooling to all components of the traction drive system, such as the

inverters

110, 112, the

traction motors

114, 116, and the like.

The alternator 104 may also be connected to a hydraulic pump 136 that provides hydraulic pressure for use by accessories or other components of the vehicle. For example, the hydraulic pump 136 may be configured to provide hydraulic pressure for use by the dipper arm 18 and/or a braking device, such as one or more

hydraulic service brakes

138, 140 associated with one or more wheels of the vehicle 10 (e.g., shown in fig. 3 as being associated with the wheels 118, 120). Although two brakes are shown in fig. 3, the vehicle may alternatively include a single brake or more than two brakes. The

hydraulic service brakes

138, 140 are operable to provide frictional braking forces or braking effort to the

wheels

118, 120 of the vehicle 10 to stop or slow the vehicle, and may be used to supplement or replace the braking effort provided by the

traction motors

114, 116 when operating in a dynamic braking mode of operation. In one embodiment, the

hydraulic service brakes

138, 140 are fluidly connected to the hydraulic pump 136 and include one or more electro-hydraulic proportional valves 144, the positions of which may be controlled by a controller, as discussed below, to control the amount of braking effort provided by the

brakes

138, 140. Other types of valves may also be utilized.

Although the vehicle 10 described herein is disclosed as including a braking device in the form of a hydraulic service brake, other types of service brakes may also be utilized on the vehicle without departing from the broader aspects of the present subject matter. For example, the service brakes may be any type of friction brake known in the art that utilizes a wear surface that contacts (e.g., clamps or presses against) a rotating or moving component of a vehicle wheel to slow or stop the vehicle by friction slowing or stopping the rotation of the wheel. The portion forcing the wear surface of the friction brake against the wheel (e.g., disc, drum, etc.) may be accomplished mechanically, hydraulically, pneumatically, or electromagnetically. As used herein, "service brakes" may include vehicle parking brakes and/or wheel brakes locks. Alternatively, the applied brakes may be one or more traction motors that are engaged to not rotate in a rearward direction (e.g., relative to a selected or previous direction of travel).

Regardless of the particular type of service brake used, the

brake devices

138, 140 may be manually deployed or activated by the operator of the vehicle, such as, for example, by depressing a brake pedal in the cab or by depressing a button on a user interface, although other means of bringing the brake into frictional contact with the rotating wheel member may also be utilized. In an embodiment, the application of the

service brakes

138, 140 may also be controlled automatically by the controller or control unit of the vehicle. In particular, as further shown in fig. 3, drive system 100 and its various components, including

brake devices

138, 140, may be electrically connected (or otherwise communicatively connected) to controller 142 and controlled by controller 142. The controller 142 may represent hardware circuitry that includes and/or is coupled to one or more processors (e.g., one or more microprocessors, field programmable gate arrays, and/or integrated circuits). In particular, the controller 142 is configured to control the traction motor system 100 and its various components, and to control the power supplied to and from the traction motor system.

As discussed below, the controller 142 is also operable to automatically prevent the vehicle from rolling backwards when on a grade through coordinated control of the

service brakes

138, 140 and the drive system 100. In particular, the control unit or controller 142 is configured to automatically apply the

service brakes

138, 140 and/or control the torque outputs of the

wheel motors

114, 116 to maintain the vehicle 10 on grade at or near zero speed during various operating conditions without input from the operator of the vehicle in order to prevent inadvertent rollback. As used herein, "automatically" means without input or intervention from an operator of the vehicle. As used herein, "rollback condition" refers to a condition or situation in which the vehicle may be moving in a direction opposite or different from the selected or desired direction of travel when no brakes are applied or the vehicle's accelerator pedal is not depressed.

For example, a rollback state is possible when the vehicle is traveling on a grade and the operator wishes to stop the vehicle. As the operator or control system releases an acceleration input device of the vehicle, such as an accelerator pedal (or otherwise manually or automatically stops accelerating in the direction of travel), the vehicle will decelerate quickly and the vehicle will approach zero speed as the vehicle is traveling on a grade. Additionally, the vehicle may slow down due to the grade in the route even if the operator continues to activate the acceleration input device (e.g., depress the pedal). When the zero speed threshold is reached, the vehicle may roll back in the absence of application of the service or parking brakes. To prevent such rearward movement, one or more brakes may be automatically activated and/or one or more motors may be automatically operated to generate torque in the opposite direction. This results in the vehicle remaining in a position on the route (e.g., not rolling backwards) or the vehicle moving slightly backwards at a controlled speed.

Movement of the vehicle in one or more directions may be determined using one or more sensors 300. These sensors 300 may include global positioning system receivers, reflective sensors, discontinuous sensors, optical encoders, variable reluctance sensors, wiegand sensors, hall effect sensors, and the like. The controller 142 may determine the direction of travel of the vehicle 10 based on the output of the sensor 300.

FIG. 4 illustrates a flow chart of an embodiment of a method 400 for preventing a vehicle from rolling backwards. The flow chart may represent operations performed under the direction of a control program executed by the controller 142 for preventing the vehicle from rolling backwards when the operator wishes to stop the vehicle on a grade. As shown therein, when the operator releases the accelerator pedal at 410, the controller 142 is configured to determine a target maximum deceleration at 412 based on the load, the vehicle speed, and/or the estimated grade, and is configured to control the torque as needed to maintain the vehicle decelerating less than the maximum deceleration rate and slow the vehicle down at 414.

The load weight may be determined based on input provided to the controller 142 by an operator, a manifest, sensors (e.g., a scale on which the load is located), etc. Vehicle speed may be determined by one or more of the sensors 300, such as a global positioning system receiver, tachometer, or the like. The estimated grade may be determined by operator-provided input or by reference to a database that includes grades at different locations of the route. Optionally, one or more of the sensors 300 may include an inclinometer, accelerometer, or the like, capable of outputting data that indicates the grade or estimated grade of the route. The target maximum deceleration (or upper deceleration limit) may be decreased for heavier loads (or may be increased for lighter loads), decreased for slower vehicle speeds (or may be increased for faster vehicle speeds) and/or decreased for smaller grades (e.g., flatter grades) or increased for steeper grades (e.g., more inclined grades) in a direction opposite the selected or previous travel direction.

The drive system 100 is used to provide a controlled deceleration/slowing of the vehicle (rather than just letting gravity control). For example, the torque generated by the motor of drive system 100 may be controlled (e.g., automatically) to achieve a target deceleration of the vehicle and reduce the speed of the vehicle to a very low but non-zero speed. The vehicle and the motor of the vehicle may continue to operate in the selected direction of travel. That is, the vehicle may not start rolling backwards downhill or stop moving to zero speed. As shown at 416, in one embodiment, the operator may then manually apply the

service brakes

138, 140 at zero speed or at a very low near-zero (but positive) speed. This may allow drive system 100 to prevent the vehicle from rolling backwards without applying any of the vehicle's brakes. For example, a vehicle may be prevented from rolling downhill backwards by torque applied by a motor of the vehicle that does not propel the vehicle in a selected direction of travel (e.g., uphill), but also prevents the vehicle from rolling downhill backwards.

As further shown in fig. 4, in an embodiment, the controller 142 may be configured to: the

service brakes

138, 140 are automatically applied when the vehicle is near zero speed under controlled deceleration, but still moving in the selected/desired direction of travel. In particular, controller 142 determines at 418 whether a brake pedal input/deceleration command (e.g., input by an operator) is present, or whether accelerator pedal feedback exceeds a threshold. If deceleration/braking is present (ON) or accelerator pedal feedback exceeds a threshold and vehicle speed is less than a threshold speed (i.e., when the vehicle is near zero speed), the controller 142 applies the

service brakes

138, 140 at 420, regardless of whether controlled deceleration or abnormal zero torque deceleration. However, if no accelerator pedal or brake feedback is received/detected, and the vehicle speed is less than the threshold speed (i.e., when the vehicle is near zero speed), the controller 142 automatically applies the

service brakes

138, 140 at 422 based on the brake delay time (i.e., the time it takes to engage the brakes and slow down/stop the vehicle) and the vehicle deceleration at the learned speed threshold at or near zero speed (but positive speed).

Further, at 424, if no accelerator pedal or brake input is received after a predetermined time has elapsed (e.g., by manual engagement of the brakes by an operator), the

brakes

138, 140 are then released. In either embodiment, the brakes may be automatically applied based on a brake delay time (i.e., the time it takes to engage the brakes and slow/stop the vehicle) and a speed threshold learned at or near zero speed (but positive speed) at which the vehicle decelerates. For example, the controller 142 may be configured to apply the brakes earlier when decelerating at a faster rate and later when decelerating at a lower rate. Accordingly, the invention described herein provides a method for preventing a vehicle from rolling backwards when stopping the vehicle on a grade, and provides a smooth transition from the vehicle moving to stopping.

Another situation where vehicle rollback may occur is to launch the vehicle on a grade. When the vehicle is stopped on a grade, the drive system typically holds the brakes. Once the vehicle is stopped, the brakes are applied, or the brakes are applied automatically during deceleration, as described above. FIG. 5 illustrates a flow chart of an embodiment of a method 500 for preventing a vehicle from rolling backwards when initiating a move on a grade. The flow chart may represent operations performed or carried out by controller 142 for preventing vehicle rollback when launching the vehicle on a grade. As shown at 510, first, the vehicle is stopped and the drive system (either by a retarding action of the traction motor or by application of a service brake (e.g., a parking brake)) holds the vehicle in a stationary position. In one embodiment, at 512, the operator applies a braking/retarding force to maintain vehicle position and depresses the accelerator pedal to increase torque to initiate movement. For example, an operator may select a direction of travel (e.g., by providing input to the control system via one or more input devices) and apply a throttle to command vehicle motion. When the torque available at the traction motor exceeds a threshold sufficient to prevent rollback (i.e., an equilibrium torque), the brakes are released and the vehicle is allowed to move in the selected direction of travel at 514. Otherwise, the brake continues to be held by the controller 142 at 516 until the torque exceeds the threshold. In one embodiment, the torque threshold may be selected based on the estimated grade.

As further shown in FIG. 5, certain fault conditions may require other measures to be taken. For example, driveline torque control and driveline braking control may not be available or usable. If such a fault condition exists, the controller 142 is configured to release the

brakes

138, 140 at 518 to prompt the operator for action. At 520, if the fault condition is resolved, the controller 142 controls the drive system 100 to respond to the operator/pedal input as usual. In another embodiment, driveline braking control may be available and functional, but driveline torque control may not. In this case, at 522, the controller 142 is configured to hold the

brakes

138, 140 during such fault conditions. If the fault is resolved, control proceeds to an initial state 510. However, if the fault is not resolved after a predetermined time, the controller 142 releases the

brakes

138, 140 at 524 while the fault is still present to prompt the operator to take action (e.g., apply the service brakes, press an override switch, control movement, etc.).

Still further referring to FIG. 5, in one embodiment, at 526, the operator may not apply any brake or acceleration input/throttle commands or the operator may release the brake (or remove the commanded retarding force). In this case, at 528, the controller 142 waits for a pedal input (e.g., deceleration/brake/throttle feedback) for a predetermined time. If a pedal input is received within the predetermined time/window, control proceeds to step 512. However, if no pedal input is received within the window, at 530, the controller 142 controls the drive system 100 to release the

brakes

138, 140, and/or remove any retarding force. In this case, the drive system 100 applies a torque at 532 to allow very low positive or negative speeds, or to allow acceleration to a predetermined speed limit, under the control of the controller 142. That is, the drive system 100 is used to allow very low speeds in the direction of gravity (i.e., limit the roll speed and prompt the operator to take some action). At 534, the very low positive or negative speed continues until the operator commands an acceleration torque or the operator stops the vehicle using the brake/deceleration pedal.

Turning now to FIG. 6, a flow diagram of one embodiment of a method 600 for controlling a vehicle during a rollback state is shown. The flow chart may represent operations performed or carried out by controller 142 during the rollback state. A rollback condition may occur, for example, due to a drive system failure (e.g., failure without propulsion), if the operator changes the selected direction of travel, or if the vehicle decelerates too quickly, crosses zero speed and begins to roll in the opposite direction before the brakes can be applied. As shown in fig. 6, 610 indicates that there is a back-slip state. In one embodiment, if the speed of the vehicle exceeds a threshold speed stored in memory (i.e., a negative speed indicating rollback) and vehicle movement is detected in a direction opposite the selected direction of travel, the controller 142 is configured to automatically control the

traction motors

114, 116 to provide a retarding force to slow the vehicle, as shown at 612. Vehicle movement in one or more directions may be determined using one or more sensors 300 shown in fig. 3. In one embodiment, the threshold speed may be about 6 mph. In one embodiment, controller 142 is configured to control drive system 100 to maintain a vehicle speed of approximately 3 mph.

As also shown in fig. 6, if the speed of the vehicle exceeds a threshold speed stored in memory (i.e., a negative speed indicating rollback) and the selector is in the neutral state, the controller 142 is configured to automatically control the

traction motors

114, 116 to provide a retarding force to slow the vehicle, as shown at 614. In one embodiment, the threshold speed may be about 5 mph. In one embodiment, controller 142 is configured to control drive system 100 to maintain a vehicle speed of approximately 3 mph.

In one embodiment, if the speed of the vehicle does not exceed the threshold speed but is still experiencing a rollback condition, the controller 142 may automatically apply the

brakes

138, 140 at 616. This may occur, for example, if the vehicle is stopped in a negative speed condition. Alternatively, at 616, the brakes may be automatically applied or otherwise activated in response to the speed of the vehicle not exceeding a threshold speed (also referred to as an upper speed limit) without a rollback condition occurring or detected. For example, if the vehicle is nearly balanced on a grade and has very low acceleration (e.g., approaching zero speed) in the expected or selected direction of travel, the brakes may be applied at some very low speed that does not exceed an upper speed limit (e.g., 30 motor revolutions per minute), regardless of whether the acceleration is or is approaching zero. This may result in the brakes being applied without the vehicle rolling back downhill or without the vehicle being detected to roll back downhill (e.g., a rollback condition). As shown at 618, the controller 142 may then automatically release the brakes and control the

traction motors

114, 116 to provide torque to allow slow creep after a fixed time. In one embodiment, if the brakes are set during a rollback condition, the operator may be required to apply and release the brakes before the vehicle is moving.

FIG. 7 shows a flow diagram of one embodiment of a method 700 for controlling movement of a vehicle. The flow diagrams may represent operations performed or carried out by the drive system 100 or the controller 142. In one embodiment, the drive system 100 may be controlled by the vehicle stopping on a grade and the drive system being holding the initial state of the brakes. The method 700 begins with a sport command 710 where the operator commands a sport by applying at least 50% throttle. In response to the sport command 710, the drive system 100 increases torque to the commanded torque or to a maximum torque (rather than just a balancing torque that holds the vehicle stationary on a grade). For example, the controller 142 may determine a torque threshold (e.g., based on an operator selected throttle setting), i.e., an amount of torque required to achieve a desired acceleration. The torque threshold may be based on the weight of the vehicle, the weight of the load carried by the vehicle, the grade on which the vehicle is parked, and the like. The drive system 100 may then increase the torque produced by the motor of the vehicle to the torque indicated by the operator or to the maximum torque that the motor is capable of producing. In an embodiment, as shown at 712, the controller 142 may control the system 100 to provide the maximum amount of available torque and automatically release the brake at the maximum torque (rather than the threshold torque for the desired speed). In another embodiment, the controller 142 may hold the brake for a predetermined (e.g., non-zero) time after the accelerator pedal is applied, and then release the brake. In this embodiment, the controller 142 applies a time delay before releasing the brakes. In another embodiment, the controller 142 may prompt the operator to release the brakes, as shown at 716. In particular, the controller 142 may indicate, for example by an audio alarm or visual display, that the operator threshold torque is available and that the system is ready to release the brakes. In yet another embodiment, the operator may control the control of the braking function. For example, at 718, the controller 142 may request the operator to apply the

service brakes

138, 140, and then automatically release the brakes upon depression of the accelerator pedal. Then, a balancing torque may be applied to maintain zero or slightly positive speed, and the torque may be increased as required by the accelerator pedal.

FIG. 13 illustrates a flow chart of an embodiment of a method 1300 for controlling movement of a vehicle from a stopped position on a grade. The operations described in connection with method 1300 may be performed or carried out by controller 142 and/or drive system 100. Method 1300 may provide a closed loop process for controlling vehicle acceleration after releasing the brakes while the vehicle is on a grade. At 1302, one or more brakes of the vehicle are engaged to hold the vehicle in place on the grade. The brake may be used according to one or more embodiments of the inventive subject matter described herein or may be engaged according to another process. At 1304, it is determined whether the brake is released. For example, the controller 142 may release the brakes in response to receiving an operator input. If the brake is released, the flow of method 1300 may proceed to 1306. Otherwise, flow of method 1300 may return to 1302.

At 1306, after and in response to releasing the brakes, the vehicle is allowed to roll back slightly and/or accelerate quickly down the grade. For example, controller 142 may allow drive system 100 to disengage the brakes without generating motor torque before directing the motor to generate torque to propel the vehicle up a grade or by generating some motor torque to allow the vehicle to roll back a small amount along a grade, such as a specified threshold distance of less than one meter (or another distance) along the length of the route. As another example, the controller 142 may direct the drive system 100 to use a motor to accelerate rapidly. The controller 142 may direct the drive system 100 to accelerate to an operator-selected or automatically-implemented throttle position faster than the drive system 100 would otherwise accelerate (e.g., when not beginning to move up a grade from a stopped position). At 1308, torque generated by the motors of the drive system 100 is rapidly adjusted to smoothly transition from a stopped vehicle position to a throttle position movement as selected by an operator or automatically implemented. For example, the abrupt acceleration implemented by drive system 100 may be reduced without vehicle jerking or other sudden movement while still moving the vehicle up a grade from a stopped position.

FIG. 14 illustrates a flow chart of an embodiment of a method 1400 for automatically controlling movement of a vehicle on a grade when no input is provided by an operator of the vehicle. The operations described in connection with method 1400 may be performed or carried out by controller 142 and/or drive system 100. At 1402, one or more brakes of the vehicle are engaged to hold the vehicle in place on the grade. The brake may be engaged according to one or more embodiments of the inventive subject matter described herein or according to another process. At 1404, it is determined whether the operator of the vehicle has provided an input within a specified blanking interval. For example, the controller 142 may determine whether the operator has depressed a brake pedal, actuated a button, or other action to provide an input to the controller 142 to maintain the brakes in an engaged state. Controller 142 may periodically check the operator input to determine whether the operator has provided input to hold the brake in the engaged state, at least once every blanking interval, e.g., every five seconds (or other time interval). If the operator has provided an input to maintain the brakes in an engaged state, the flow of method 1400 may return to 1402. Otherwise, if the operator does not provide input within the blanking interval, the flow of method 1400 may proceed to 1406.

At 1406, the brakes of the vehicle are released. At 1408, motor torque is generated to move the vehicle up the grade in a slow creep manner. For example, while the brakes of the vehicle are disengaged (or shortly thereafter), controller 142 may direct the motors of drive system 100 to begin generating a small amount of torque to move the vehicle up the grade at a slow speed (e.g., less than five kilometers per hour).

In certain embodiments, both the operator and the automatic control may be used for the transition from stopped to moving in the selected direction of travel without unexpected rollback, as illustrated by the flow chart of method 800 shown in fig. 8. For example, as discussed above in connection with fig. 4, after the operator releases the accelerator pedal, the controller 142 may determine a target maximum deceleration and control the drive system to provide torque as needed to limit the maximum deceleration rate. This allows the vehicle to be decelerated to a very low speed and the commanded direction of travel to be maintained, as shown at 810. The operator may then apply the service brakes or parking brakes at zero speed to maintain the vehicle at a standstill, as shown at 812. From this stationary state, various control strategies are considered that allow a certain level of operator input when transitioning from the stationary state to movement in the selected direction of travel.

The first control strategy 820 includes the operator setting the wheel locks and releasing the previously applied service or parking brakes to hold the vehicle stationary on the grade 822. As shown at 824, both manual and automatic control are then used to smooth the vehicle transition from stopped to the selected direction of travel when accelerator feedback is detected. In particular, the controller 142 is configured to first command the drive or park brakes to be on when the wheel lock is in the on state (from step 822) and the accelerator pedal feedback exceeds a threshold. The operator may then be prompted to unlock the wheel lock. Once the wheel lock is turned off, the controller 142 is configured to automatically release the service or parking brake when the available torque threshold is met, as discussed in the above embodiments (i.e., when sufficient torque is available to prevent rollback).

The second control strategy 830 includes the controller 142 automatically applying the service brakes at 832 after the operator applies the brakes to bring the vehicle to zero speed. As discussed in the above embodiments, at 834, the controller 142 is configured to automatically release the brakes when the operator applies the accelerator pedal and the available torque exceeds a threshold level sufficient to prevent the vehicle from rolling backwards. The control allows the vehicle to transition from a stationary state to a smooth movement in the selected direction of travel.

Likewise, the third control strategy 840 includes the controller 142 automatically applying the service brakes at 842 after the operator applies the brakes to bring the vehicle to zero speed. The operator may then hold the brake and apply the accelerator pedal to begin moving the vehicle on a grade. In conjunction with this, the controller 142 is configured to automatically release the brakes when the available torque exceeds a threshold level sufficient to prevent the vehicle from rolling backwards, as shown at 834. In one embodiment, the brake pressure may be slowly reduced as the balancing torque is applied.

In one embodiment, when starting the vehicle on a grade, the operator (in manual start mode) or controller 142 (in automatic start mode) may balance both brake and torque application with a variably applicable hydraulic brake or a hydraulic brake with a flow restriction valve to prevent rollback. With increasing torque, the brake may be slowly released, for example by reducing brake pressure. In this way, the brake operates like a clutch, balancing torque and brake application to prevent the vehicle from rolling backwards and smoothly transitioning to positive motion. In one embodiment, the brake may be a hydraulic brake having an associated flow limiting valve that is controllable by the controller 142 such that brake pressure may be selectively reduced as torque increases. The rate of torque increase (ramp rate) can be adjusted to match the known brake pressure and brake torque rate to maintain zero speed. The system may be configured to continue to adjust the rate of increase of applied torque and the brake pressure drop until the brakes are fully released. In both cases (i.e., a variable application hydraulic brake or a hydraulic brake with a flow restriction valve), continued application of torque effects movement of the vehicle after the brake is fully released. If excessive vehicle movement (e.g., acceleration too fast) indicative of a fault condition is detected, the brakes may be automatically applied to stop vehicle motion.

In addition to ensuring that the vehicle is prevented from rolling backwards when stopped on grade and when started on grade, the system and method of the present subject matter also allow for increased level of control over the transition from forward motion to reverse motion, and vice versa. For example, when the drive system inverter is turned off, the operator may request a change in direction at speed by changing the selector to the opposite direction (e.g., forward to reverse, or reverse to forward), rather than commanding neutral. In this case, the controller 142 is configured to determine whether to enter deceleration based on the gravity estimation and the vehicle acceleration. In one embodiment, controller 142 controls drive system 100 to provide a controlled deceleration to zero speed if traveling down a steep grade. In particular, the controller 142 is configured to deny the granting of the drive torque in the requested direction if the vehicle speed exceeds the threshold and the vehicle is traveling in a direction opposite the requested direction. Once the vehicle speed is reduced below the threshold value using controlled deceleration, the controller 142 is then configured to apply the brakes based on the received torque command, the torque threshold on the grade, and the vehicle speed such that the brakes are held until the available torque in the newly selected direction of travel is sufficient to prevent the vehicle from rolling backwards.

However, if the vehicle is traveling on a relatively flat surface, the controller 142 controls the drive system to switch to a deceleration mode based on vehicle speed and acceleration and interprets the accelerator pedal feedback as a deceleration command. The drive system 100 automatically stops the vehicle with the service brakes based on the received torque command, the torque threshold on the grade, and the vehicle speed, such that the brakes are held until the available torque in the newly selected direction of travel is sufficient to prevent the vehicle from rolling backwards. If the push command is insufficient to prevent rollback, the brakes are applied and held to prevent rollback. If the propulsion command is sufficient to prevent rollback, the vehicle is allowed to transition to drive in the manner described above.

Optionally, drive system 100 and the accompanying method described herein may prevent the vehicle from rolling backwards on a grade by applying a direct current to an alternating current motor of the vehicle. The controller 142 may determine the specified dc amount from a previously determined amount or based on the load, the grade, and/or the speed of the vehicle (moving up the grade). For heavier loads, steeper grades, and/or faster speeds, the controller 142 may calculate a greater amount of dc. For lighter loads, flatter grades, and/or slower speeds, the controller 142 may calculate a smaller dc amount.

A determined amount of direct current is then applied or provided to one or more alternating

current motors

114, 116 of the drive system 100. In an embodiment, the dc amount applied to the

motors

114, 116 is the maximum dc amount that the drive system 100 can provide to the

motors

114, 116. Alternatively, the dc amount applied to the

motors

114, 116 is less than the maximum dc amount that the drive system 100 can provide to the

motors

114, 116. This current is applied to the

motors

114, 116 without engaging or otherwise activating the brakes of the vehicle. The direct current provided to the

motors

114, 116 prevents the

motors

114, 116 from moving in the opposite direction (e.g., to cause or allow the vehicle to roll down a grade backwards). In this manner, the direct current causes the

motors

114, 116 to operate as brakes without applying any brakes of the vehicle. Optionally, one or more brakes of the vehicle may also be applied to maintain the position of the vehicle.

The application of the brakes (or any brakes previously applied) may be released as direct current continues to be provided to the

motors

114, 116. For example, the controller 142 may activate or otherwise control switches that can control the flow of direct current to the

motors

114, 116. Disengaging the brakes of the vehicle while maintaining the application of direct current to the

motors

114, 116 can prevent the vehicle from rolling backwards down the grade as the

motors

114, 116 transition to anti-skid control and generate a holding torque that can counteract the force of gravity pulling the vehicle down the grade.

Alternatively, the controller 142 may apply maximum or 100% of the alternating current to the

motors

114, 116 before the vehicle is about to stop on grade or roll back, and then apply one or more brakes of the vehicle before the vehicle reaches a full stop. For example, when the vehicle is moving up a grade, the controller 142 may increase the ac provided to the

motors

114, 116 to the maximum amount that the drive system 100 can provide to the motors 114, 116 (without damaging the motors 114, 116), and then apply the brakes of the vehicle when the vehicle reaches a complete stop (e.g., when the speed of the vehicle is zero).

In another embodiment, controller 142 may operate as a speed regulator when the vehicle is traveling up a grade and is about to stop. The controller 142 may control the torque generated by the

motors

114, 116 while the vehicle is decelerating and traveling at a low speed (e.g., no greater than six kilometers per hour or another speed). The controller 142 can provide current to the

motors

114, 116 at the base excitation frequency of the

motors

114, 116 to control the

motors

114, 116 and stop the vehicle on grade without the vehicle rolling back down the grade.

In another embodiment, the present subject matter provides a system and method for reducing the speed of a vehicle using a retarding force provided by a traction motor of the vehicle. For example, first, the vehicle may be moving in a desired direction of travel, and the operator may request full/maximum retarding effort to stop the vehicle. If the deceleration requirement is to effect deceleration of the vehicle by means of a lever or other means that does not require the operator to actively hold the lever, the traction motor decelerates the vehicle to and maintains a low, near zero speed. If the deceleration request is through a rebound pedal or similar mechanism, the traction motor decelerates the vehicle to a low, near zero speed and then the vehicle is stopped with the service brakes. In one embodiment, the operator may then hold the vehicle at a stop using the service brakes or the parking brakes. In one embodiment, in use, the operator may hold the vehicle at a stop by continuing to depress the retarder pedal. In this case, if the operator then releases the decelerator pedal, the controller 142 is configured to command the traction motor to maintain a stopped state (zero speed) for a predetermined amount of time. If the vehicle is equipped with an override switch, the accelerator pedal allows rollback speed to be controlled by deceleration when depressed after a time delay. If the vehicle does not have an override switch, the vehicle is allowed to accelerate to an opposite motion threshold. If the operator applies the accelerator pedal, the zero speed condition will continue to be maintained until a sufficient amount of torque is available to prevent rollback and to move the vehicle in the intended direction of travel, as described above.

In conjunction with the above, in one embodiment, the vehicle may include an override switch configured to send an override signal to the controller 142 to enable the operator to disable the set control procedure described above. For example, at various times during operation of the vehicle, the operator may wish to take over full control of the vehicle rather than having the controller 142 instruct the vehicle to accelerate, decelerate, stop, and move. In particular, the operator may want to be able to slide in a direction opposite to the selected driving direction, for example when turning on a gentle slope. In this case, the operator may press an override button or otherwise be able to enable an override to disable the automatic application brake function described above and allow for coast-back. In one embodiment, the controller 142 may still be configured to automatically apply the brakes or utilize the traction motors to slow or stop the vehicle if the rollback caused by the override results in an overspeed or over-acceleration condition (i.e., speed or acceleration exceeds a safety threshold).

In one embodiment, the system of the inventive subject matter also includes a redundant braking or notification function that is automatically implemented in the event of a drive system failure or malfunction. For example, when the vehicle is on a grade, if the drive system card suddenly fails or is powered down, roll back will occur if the system does not apply the brakes. In such a scenario, the operator may not notice and may think that the brakes will be automatically applied according to the automatic control described above to prevent rollback. Thus, the system may be equipped with a redundant braking function that will be automatically implemented before or after a rollback condition when a drive system fault is detected and vehicle speed exceeds a threshold. In one embodiment, a brake may be applied to control deceleration to zero speed. In one embodiment, the system may also be configured to output an audible or visual warning to the operator to inform the operator that the anti-rollback control described herein will not work. This provides an alert to the operator that the drive system will not be able to apply the brake and that manual operation is necessary to prevent a rollback condition. This protection ensures that the operator can notice and alert the operator that the automatic anti-rollback functionality is not available.

In one embodiment, the control system of the inventive subject matter, by utilizing the above functionality, is configured to provide controlled deceleration of the vehicle and automatic engagement of the service brakes while the vehicle is still moving in the intended direction of travel to prevent the vehicle from rolling backwards when stopped. That is, the service brakes are applied in accordance with the acceleration/deceleration of the vehicle prior to crossing zero speed. The system of the inventive subject matter is further configured to prevent rollback when launching the vehicle from a stop on grade by determining a torque threshold to achieve a desired acceleration (rather than speed) or by performing a maximum or preset target torque launch rather than a threshold torque launch. Due to the control strategy presented herein, vehicles using the control system of the inventive subject matter are more user friendly and require less skill to operate. Additionally, the control system of the inventive subject matter can update an existing vehicle by modifying the control software without extensive hardware upgrades or modifications.

In one embodiment, a method for controlling a vehicle is provided. The method comprises the following steps: controlling at least one traction motor of the vehicle to provide controlled deceleration of the vehicle when traveling on a grade in a selected direction of travel, and automatically applying service brakes of the vehicle when the vehicle is moving in the selected direction of travel.

In another embodiment, a system is provided. The system comprises: a control unit configured to be electrically connected to a drive system of the vehicle, the drive system comprising at least one traction motor for providing motive power to the vehicle and service brakes associated with at least one wheel of the vehicle. In the absence of a command to provide motive force in the selected direction of travel, the control unit is configured to automatically apply the service brakes when the vehicle is moving in the selected direction of travel to prevent the vehicle from rolling backwards.

In one embodiment, controller 142 is also operable to prevent the vehicle from rolling backwards when on grade or when pushing a mound by automatic application of

service brakes

138, 140. When using an existing LHD vehicle 10 to propel a mound of earth, for example, after the operator releases the accelerator pedal and before he/she can manually engage the service brakes, the spring tension in the dipper arm 18 and the slope the vehicle is at in the mound of earth may cause the vehicle to inadvertently roll back several feet. However, in accordance with an embodiment of the inventive subject matter described herein, the control unit or controller 142 is configured to automatically apply the

service brakes

138, 140 upon detection of a rollback condition to maintain the vehicle 10 at or near zero speed on grade and/or while pushing the top soil/burden pile, without input from the operator of the vehicle, in order to prevent such inadvertent rollback. As used herein, "automatically" means without input or intervention from an operator of the vehicle. As used herein, "rollback condition" refers to a condition or state of movement of the vehicle in a direction opposite or different from the selected or desired direction of travel that is possible in the absence of braking or in the absence of depression of the vehicle's accelerator pedal.

For example, in one embodiment, the controller 142 is configured to continuously or intermittently monitor or detect a selected direction of travel (i.e., forward or reverse) of the vehicle and a speed of a motor (e.g., one or more of the traction motors) and to immediately command engagement of the

service brakes

138, 140 associated with the

wheels

118, 120 of the vehicle 10 when a rollback condition is detected. In one embodiment, a "rollback condition" exists when the motor speed in a direction opposite or different from the selected direction of travel exceeds a predetermined threshold. As used herein, "opposite or different from a selected direction of travel" refers to, for example, the motor rotating in a direction opposite to that required to effect movement of the vehicle in the selected direction of travel or in a mode other than that required to propel the vehicle in the selected direction of travel (e.g., a regenerative braking mode).

In one embodiment, the threshold motor speed, which is the direction of travel opposite or different from the direction of travel prompting automatic application of the service brakes to prevent rollback, may be between about 0rpm and about 100 rpm. In another embodiment, the threshold speed may be between about 10rpm to about 90 rpm. In another embodiment, the threshold motor speed may be between about 20rpm to about 80 rpm. In another embodiment, the threshold motor speed may be between about 30rpm to about 70 rpm. In another embodiment, the threshold motor speed may be between about 40rpm to about 60 rpm. In yet another embodiment, the threshold motor speed may be about 50rpm in a direction opposite the selected direction of vehicle travel.

In one embodiment, the vehicle 10 has a fixed gear ratio of approximately 90:1 such that the 50rpm threshold (in a direction opposite the selected direction of travel) at which the service brakes are engaged is not perceived by the observer or operator as moving. In one embodiment, the controller 142 is configured to apply the

service brakes

138, 140 to prevent rollback within approximately 100 milliseconds of detecting the vehicle rollback condition. In one embodiment,

brakes

138, 140 may be maintained in a fully open or engaged state by controller 142 until the selected direction of travel is changed by the operator to match the direction of the motor and/or the accelerator pedal is depressed or activated by the operator.

Referring now to FIG. 9, a method 200 of controlling a vehicle to prevent the vehicle from rolling backwards is shown, according to an embodiment of the present invention. As shown therein, at 202, a selected direction of travel of the vehicle is detected and recorded by the controller 142. The speed and direction of at least one traction motor (e.g.,

motors

114, 116 of vehicle 10) is also monitored. At 204, the controller 142 determines whether the direction of the motor is opposite the selected direction of travel. If not, no automatic measures are taken in connection with the application of the service brakes. If the motor direction is opposite the selected travel direction, the controller 142 then (or simultaneously) determines if the motor speed exceeds the threshold speed at 206. If not, no automatic measures are taken in connection with the application of the service brakes. However, if the motor detected speed in the direction opposite the selected direction of travel exceeds the threshold speed, at step 208, the controller 142 automatically engages the service brake to prevent the vehicle from rolling backwards. As described above, the service brakes remain engaged until the operator of the vehicle changes the selected direction of travel to match the motor direction and/or the accelerator pedal is depressed by the operator.

FIG. 10 illustrates a graph 1000 showing operation of the vehicle rollback prevention system, with line 1002 representing motor speed, line 1004 representing brake percentage on, line 1006 representing the "reverse" selected direction of travel, line 1008 representing the "forward" selected direction of travel, and line 1010 representing depression of the accelerator pedal. At 1012, the forward motor speed exceeds a threshold motor speed of 50rpm while the vehicle is operating in the reverse selected direction of travel. At 1014, the service brakes are then automatically activated by the controller to 100% engaged/open to prevent the vehicle from rolling backwards. At 1016, the operator (or controller automatically) switches the vehicle from reverse to forward, and depresses the accelerator pedal at 1018 to move the vehicle forward. At 1020, control then disengages the service brakes.

In one embodiment, the control system or controller of the present invention, by utilizing the above functionality, is configured to automatically engage the service brakes whenever a rollback condition is sensed. This prevents the vehicle from rolling backwards on a grade or when pushing a mound of earth, etc., without operator input or action, and ensures that movement of the vehicle in directions other than the selected direction is not possible when the vehicle is in a forward or reverse direction. By managing vehicle movement in this manner, the control system of the present subject matter ensures that rollback or vehicle movement in directions other than the selected direction can be prevented. Thus, vehicles using the control system of the present subject matter are more user friendly and require less skill to operate. Additionally, the control system of the present subject matter may be retrofitted (or added) to existing vehicles by modifying the control software (e.g., to direct the controller to function as described herein) without extensive hardware upgrades or modifications.

In one embodiment, a method for controlling a vehicle is provided. The method comprises the following steps: the method includes determining a selected direction of travel of the vehicle, monitoring a direction of travel of a motor of the vehicle, monitoring a speed of the motor, and automatically applying a service brake of the vehicle when a rollback condition is detected to prevent the vehicle from rolling backwards. In one embodiment, a rollback condition exists when the direction of travel of the motor is different from the selected direction of travel. In one embodiment, a rollback condition exists when the speed of the motor exceeds a threshold speed. In one embodiment, the vehicle is a load-transport-unload vehicle. In one embodiment, the service brake is a hydraulic or pneumatic service brake. In an embodiment, the method may further comprise the step of disengaging the service brake when the selected direction of travel matches the direction of operation of the motor and the accelerator pedal of the vehicle is depressed. In one embodiment, the threshold speed is between about 0rpm and about 100 rpm. In other embodiments, the threshold speed is between about 40rpm and about 60 rpm. In other embodiments, the threshold speed is about 50 rpm. In one embodiment, the vehicle has a fixed gear ratio of about 90: 1.

In another embodiment, a system is provided. The system comprises: a control unit configured to be electrically connected to a drive system of a vehicle, the drive system including at least one traction motor for providing motive power to the vehicle; and a service brake associated with at least one wheel of the vehicle. The control unit is configured to automatically apply the service brakes when a rollback state is detected, to prevent the vehicle from rolling backwards. In an embodiment, the control unit is configured to monitor the direction of operation of the at least one traction motor and the speed of the at least one traction motor. In one embodiment, the rollback condition exists when the direction of operation of the at least one traction motor differs from the direction of operation of the motor corresponding to the selected direction of travel of the vehicle and the speed of the at least one traction motor exceeds a threshold speed. In one embodiment, the control unit is configured to disengage the service brake when the selected direction of travel matches the direction of operation of the at least one traction motor and the accelerator pedal of the vehicle is depressed. In one embodiment, the service brakes are pneumatic or hydraulic brakes. In one embodiment, the threshold speed is about 50 rpm. In one embodiment, the vehicle has a fixed gear ratio of about 90: 1.

In other embodiments, a vehicle is provided. The vehicle includes a drive system including a traction motor drivingly connected to wheels of the vehicle, the motor configured to provide motive force to propel the vehicle in a selected direction of travel in a propulsion mode of operation; a controller electrically connected to the drive system; and a friction brake associated with at least one wheel of the vehicle. The controller is configured to automatically engage the friction brake when a rollback condition is detected to prevent the vehicle from rolling backwards. In one embodiment, the controller is configured to monitor the direction of operation of the motor and the speed of the motor. In one embodiment, the rollback condition exists when the direction of travel of the motors is different from the selected direction of vehicle travel and the speed of at least one of the traction motors exceeds a threshold speed. In one embodiment, the threshold speed is about 50rpm and the vehicle has a fixed gear ratio of about 90: 1. In one embodiment, the vehicle is a load-transport-unload vehicle.

Additional embodiments of the inventive subject matter relate to control systems and methods (e.g., brake control) for controlling transitions from friction brakes to electrical power (and vice versa) within a vehicle to automate the operation of starting and stopping of the vehicle on inclined (greater than zero degree) grades. According to one aspect, for example, a control system (and associated method) is configured to simultaneously control an electric drive system and a friction brake system of a vehicle to prevent rollback when operating the vehicle for movement from a stopped position on an inclined grade. According to another aspect, a control system (and associated method) is configured to simultaneously control an electric drive system and a friction braking system of a vehicle while traveling on an inclined grade to stop the vehicle and maintain the vehicle at a stop.

Another embodiment of an electric drive system 100 is shown in fig. 11. The electric drive system 100 is at least partially housed within the vehicle 10, 30 and includes a three-phase Alternating Current (AC) generator/alternator 1108 connected to be mechanically driven by an engine 1106 (e.g., a diesel engine). The AC output of the generator 1108 is supplied to one or more rectifiers 1110 configured to convert the AC output of the generator/alternator 1108 to a Direct Current (DC) output. The DC output of the rectifier 1110 is supplied to a DC bus, which (among other loads) is supplied to a set of

inverters

1112, 1114.

Inverters

1112, 1114 are configured to convert DC power from the DC bus to controlled three-phase variable frequency AC power. The outputs of

inverters

1112, 1114 are electrically connected to electric motors 1102, 1104 (respectively), and the AC power output by

inverters

1112, 1114 has a waveform suitable for driving

electric motors

1102, 1104. The

electric motors

1102, 1104 are operatively connected to drive wheels (e.g., rear wheels) of a first set of wheels of the vehicle. For example, the

motors

1102, 1104 may be three-phase AC induction wheel motors. If the second set of wheels of the vehicle are drive wheels, the electric drive system 100 may include additional inverters and motors connected in a manner similar to

inverters

1112, 1114 and

motors

1102, 1104 of FIG. 11.

As further shown in fig. 11, a drive system control unit or controller 1116 is electrically connected to the electric drive system 100. For example, a drive system control unit may be connected to the

inverters

1112, 1114. Among other tasks, the drive system control unit 1116 is configured to determine a desired torque request signal and send the desired torque request signal to the

inverters

1112, 1114. The torque demand signal is processed by the control unit for the

inverters

1112, 1114 to drive the

motors

1102, 1104 to a desired torque output level, and in a desired rotational direction corresponding to the desired direction of vehicle movement. The control unit is also configured to control the

motors

1102, 1104 to provide retarding tractive effort to the wheels (e.g., rear wheels) to slow or stop the vehicle. In particular, when operating in an electric braking mode, also referred to as electric retarding, the

electric motors

1102, 1104 reverse to charge the generator, and the drive wheels of the vehicle drive the

electric motors

1102, 1104. The

drive motors

1102, 1104 exert torque on the drive wheels and cause them to slow, thereby braking the vehicle. In one embodiment, the control unit 1116 includes one or more microprocessors that operate in accordance with a set of stored instructions to provide vehicle control, as discussed in detail below and elsewhere herein.

Fig. 12 illustrates an embodiment of a control system (e.g., a brake control system) or control unit 1116 in more detail. The control system 1116 includes a friction brake system 1222 that includes a first (e.g., rear) friction brake unit 1220 (e.g., friction brake actuation unit) associated with a first set of wheels 1212 (e.g., rear wheels) of the vehicle and a second (e.g., front) friction brake unit 1218 (e.g., friction brake actuation unit) associated with a second set of wheels 1214 (e.g., front wheels) of the vehicle. In one embodiment, friction brake system 1216 is a hydraulic brake system that further includes a first (e.g., rear) brake solenoid valve 1226 and a second (e.g., front) brake solenoid valve 1224, the first brake solenoid valve 1226 being controllable to control the pressure of hydraulic oil applied to the first friction brake unit 1220, the second brake solenoid valve 1224 being controllable to control the pressure of hydraulic oil applied to the second friction brake unit. In other embodiments, other means for activating the first and second

friction brake units

1218, 1220 may also be utilized without departing from the broader aspects of the present subject matter. In either (or either) embodiment, each friction brake unit may include, for example, various components for controllably applying a frictional load to moving members associated with the

wheels

1212, 1214, such as brake pads operatively connected to the axle or brake disc/rotor, hydraulically actuated calipers for applying force to the brake pads against the disc/rotor, and the like. The control system 1116 further includes a friction brake control unit 1227 configured to control application of the first and second (e.g., rear and front)

friction brake units

1220, 1218 at least partially in response to operator input, such as depression of a brake pedal.

In an embodiment, the drive system control unit 1116 and the friction brake control unit 1227 are electrically connected to each other and may be generally referred to as one or more controllers 1229. Although the drive system control unit 1116 and the friction brake control unit 1227 are shown as separate components in fig. 12, the

control units

1116, 1227 may be integrated into a single control unit/controller/processor without departing from the broader aspects of the present subject matter.

As further shown in fig. 12, the drive system control unit 1116 is electrically connected to a driveline 1228 of the vehicle 10, which includes the electric drive system 100, e.g., the engine 1106, the generator 1108, the rectifier 1110, the

inverters

1112, 1114, and the drive motors 1102, 1104 (AC induction wheel motors as shown in fig. 11 or otherwise). When braking the vehicle 10 in the electric retarder braking mode, the control unit 1116 commands the electric drive system 100 (which in effect acts as an electric retarding system, including

inverters

1112, 1114 and motors 1102, 1104) to provide the required vehicle retarding torque to the wheels.

As also shown in fig. 12, one or both of the drive system control unit 1116 and/or the friction brake control unit 1227 may be configured to receive inputs from operator controls 1233 (e.g., an ignition switch 1234, an accelerator position sensor 1236, a brake pedal position sensor 1238, and/or a gear selector 1240) for operating the

electric motors

1102, 1104 to propel and brake the vehicle 10. Ignition switch 1234 is operable to start and shut off the vehicle. The accelerator position sensor 1236 is configured to detect a position of an accelerator pedal or other actuator. The brake pedal position sensor 1238 is configured to detect a position of a brake pedal or other actuator. The gear selector 1240 provides a means for allowing the operator to select a desired or expected direction of vehicle movement, such as forward or reverse movement. Additionally or alternatively, the operator controls may include additional types of input interfaces 1242, such as a steering wheel or other steering device, a touch screen or other computer interface, control inputs from a control system or automation controller, and so forth. As further shown in fig. 12, a display 1244 may be electrically connected to the drive system control unit 1116 to allow an operator of the vehicle 10 to view status information related to various vehicle systems. The display 1244 and operator controls 1233 collectively form an I/O (input/output) system 1245.

With further reference to FIG. 12, the control system 1116 is configured to automate operation of the vehicle when starting and stopping on a grade while in a loaded state. In operation, when an operator of the vehicle (the operator may be a human or an automatic controller) requests that the vehicle be stopped or that the vehicle be moved in a certain direction (e.g., in both cases, by operator control), the drive system control unit 1116 communicates with the friction brake control unit 1227 to control the transition from friction brakes to power/propulsion, and vice versa. In particular, the control system includes an interface between the drive system control unit 1116 and the friction brake control unit 1227 that allows the drive system control unit 1116 (e.g., in response to feedback or other information from the electric drive system 100) to request a particular braking effort from the friction brake control unit 1227. This interface also allows the drive system control unit 1116 to request the addition or removal (i.e., increase or decrease) of friction braking effort from the friction braking unit 1227. As such, in an embodiment, the drive system control unit 1116 is configured to communicate with the friction brake control unit 1227 to control the amount of friction brake application during vehicle stopping and starting. For example, the drive system control unit 1116 may be configured to communicate with the friction brake control unit to at least partially automatically control the amount of friction brake application during vehicle stop and start on an incline grade on which the vehicle is located. (at least partially automatically controlled means fully automatically controlled, or automatically controlled in response to and based in part on operator input, e.g., a level or rate of braking or acceleration in response to and proportional to a degree of change in position of a brake pedal or accelerator pedal.)

In conjunction with the above, the drive system control unit 1116 is configured to use the system parameters to calculate the force required to maintain the vehicle on a given grade of incline. The drive system control unit 1116 then determines when it is desired to release the friction brakes or add more friction braking effort based on this determined force. This force can be determined based on various methods as outlined in the above-mentioned U.S. patent application No.14/464,226, filed on 8/20, 2014. Alternatively or additionally, the control unit 1116 may be configured to determine the force based on information of the grade of incline generated by the onboard inertial measurement unit, vehicle mass information (e.g., determined by a weigh station, or onboard, physics-based calculations of sensor data related to vehicle acceleration under known conditions), other vehicle/system parameters (e.g., wheel radius of the vehicle), and so forth.

In an embodiment, control system 1116 is further configured to provide an anti-rollback function. In particular, the drive system control unit 1116 is configured to determine the torque level required to move the vehicle up a grade of incline from a stop (i.e., the vehicle is stopped while on a grade of incline and then controlled to move up a grade of incline). The torque level may be determined based on the force, e.g., the torque level will be a level at least just exceeding the force. At the time the required torque is calculated (or at some point after the torque is calculated), the drive system control unit 1116 communicates with the friction brake control unit 1227 to request that the friction brake application be removed (i.e. the amount of friction brake application is zero) to initiate movement of the vehicle in the desired direction without significant rollback. As such, in an embodiment, drive system control unit 1116 is further configured to communicate with friction brake control unit 1227 in response to input from an operator control (for the vehicle to move up and down an incline grade) to remove a friction brake application, and at the same time control electric drive system 100 to provide electric motive force for the vehicle to move up (or down) the incline grade from a stop without significant vehicle rollback, according to the determined torque level.

The drive system control unit 1116 may be configured to communicate with the electric drive system and the friction brake control unit such that the amount and rate of friction brake application removed (by the friction brake control unit controlling the friction brake system) is automatically controlled to be proportional or equal to the amount and rate of additional torque provided (by the electric drive system controlled by the drive system control unit). For example, as the friction brake application is reduced by a particular amount, while the torque is increased by at least an amount sufficient to offset the reduced friction brake application to prevent the vehicle from rolling backwards until the friction brake application is completely removed, at which point additional torque is generated for moving the vehicle forward. (No "significant" vehicle rollback includes no vehicle rollback and vehicle rollback below a threshold deemed to still meet specified safety criteria, e.g., rollback of no more than 0.3 meters for some haul truck applications.)

In other embodiments, the control system is alternatively or additionally configured to provide a controlled stop function, such as when the vehicle 10 is operating on a grade. In particular, the drive control unit 1116 is configured to calculate the force required to hold the vehicle on a given inclined grade, and in response to input from the operator control to stop the vehicle while moving on the grade, communicate with the friction brake control unit 1227 to increase the amount of friction brake application based at least in part on the determined force to stop the vehicle and to keep the vehicle stopped on the grade. The drive system control unit 1116 may be further configured to first calculate the force required to bring the vehicle to a stop and, at the same time, communicate with the friction brake control unit 1227 to request the amount (and rate) of friction brake application to stop and then hold the vehicle on an incline grade. Typically, such calculations may take into account vehicle mass, current rate/speed of travel, degree of grade incline, and the like. For example, the braking force required to stop the vehicle when traveling up a grade will depend on the vehicle mass and the rate of deceleration (the speed changes from the current speed to zero over a given distance) since the rolling friction/drag is less than that due to gravity on the grade. The braking force required to hold the vehicle on grade will then depend on the vehicle mass, grade, etc., as described above.

In an embodiment, application of the friction braking system to stop the vehicle and to keep the vehicle stopped on an inclined grade occurs simultaneously with the electrical deceleration. Here, the drive control unit 1116 is configured to calculate the force required to maintain the vehicle on a given inclined grade and, concurrent with the reduction in electrical deceleration, communicate with the friction brake unit to increase the amount of friction brake application based at least in part on the determined force, bring the vehicle to a stop and maintain the vehicle stopped on the grade. As such, the drive system control unit 1116, in response to an input from the operator control for vehicle stop, may be configured to initially initiate electrical deceleration as the vehicle moves up the grade of incline, and to simultaneously communicate with the friction brake control unit to increase the amount of friction brake application as the deceleration effort through the electric drive system decreases as the vehicle slows. After the vehicle reaches a full stop, the amount of electrical deceleration may be zero, and in such a case, the amount of friction brake application will be sufficient to keep the vehicle stopped on an incline grade. The drive system control unit 1116 may be configured to automatically control the amount and rate of increase in friction brake application concurrent with the reduction in electrical deceleration such that: (i) the overall deceleration profile of the vehicle (the speed changing over time from the current non-zero speed to zero speed) is linear (and thus appears smooth to a human operator); and (ii) proportional in rate to one or more inputs from the operator control, e.g., the drive system control unit will control a reduction in electrical deceleration while increasing friction braking to provide a faster deceleration in response to an input from the operator control requiring a higher level/rate of braking relative to an input from the operator control requiring a lower level/rate of braking.

In an embodiment, the control system is configured both for controlled stopping of the vehicle on an inclined grade and for preventing rollback when the vehicle is controlled to move forward from its stopped position (e.g. up a grade). Here, the drive control unit, in response to a first input from the operator control for stopping while the vehicle is moving on a grade, is configured to determine a force (to hold the vehicle stopped on the grade) and communicate with the friction brake control unit (e.g., concurrently with the reduction in electrical deceleration) to increase the amount of friction brake application based at least in part on the determined force, to stop the vehicle and to hold the vehicle stopped on the grade. The drive system control unit is further configured to determine a torque level required to move the vehicle up the grade from a stop. A drive system control unit, responsive to a second input at the operator control for moving the vehicle up the grade of incline, further configured to: communicating with a friction brake control unit to remove a friction brake application; and at the same time controlling the electric drive system to provide electric power for the vehicle to move from a stop to up an incline grade according to the determined torque level without significant vehicle rollback.

In another embodiment, a method of controlling a vehicle includes, at a drive system control unit of the vehicle, controlling an electric drive system associated with at least a first set of wheels of the vehicle to selectively provide electrical motive power to the at least first set of wheels to propel the vehicle and to electrically slow the vehicle. The method further includes, at the drive system control unit, determining a torque level required to move the vehicle from a stop to up the grade of incline. The method further includes, at the drive system control unit, in response to input from the operator control for moving the vehicle up the grade, communicating with a friction brake control unit of the vehicle to remove a friction brake application holding the vehicle stopped and simultaneously controlling an electric drive system of the vehicle to provide an electric motive force according to the determined torque level for moving the vehicle up the grade from stopped without significant vehicle rollback.

In another embodiment, a method of controlling a vehicle includes, at a drive system control unit of the vehicle, controlling an electric drive system associated with at least a first set of wheels of the vehicle to selectively provide electrical motive power to the at least first set of wheels to propel the vehicle and electrically slow the vehicle to slow the vehicle. The method further includes, at the drive system control unit, determining a force required to maintain the vehicle on an incline grade on which the vehicle is located. The method further includes, at the drive system control unit, communicating with a brake control unit of the vehicle to reduce or increase an amount of friction brake application applied to at least one of the first set of wheels or the second set of wheels of the vehicle based at least in part on the determined force to hold the vehicle on the grade of incline.

In another embodiment, a method of controlling a vehicle includes, at a drive system control unit of the vehicle, controlling an electric drive system associated with at least a first set of wheels of the vehicle to selectively provide electrical motive power to the at least first set of wheels to propel the vehicle and electrically slow the vehicle to slow the vehicle. The method further includes, at the drive system control unit, determining a force required to maintain the vehicle on an incline grade on which the vehicle is located. The method further includes, at the drive system control unit, communicating with a brake control unit of the vehicle to reduce or increase an amount of friction brake application applied to at least one of the first set of wheels or the second set of wheels of the vehicle based at least in part on the determined force to hold the vehicle on the grade of incline. The method also includes, at the drive system control unit, receiving input from an operator control for stopping the vehicle while traveling on the grade. A force is determined in response to the received input. The method further comprises the following steps: at the drive system control unit, communication is made with the friction brake control unit to increase the amount of friction brake application to stop the vehicle and stop the vehicle on a grade based at least in part on the determined force.

In another embodiment, a method of controlling a vehicle includes, at a drive system control unit of the vehicle, controlling an electric drive system associated with at least a first set of wheels of the vehicle to selectively provide electrical motive power to the at least first set of wheels to propel the vehicle and electrically slow the vehicle to slow the vehicle. The method further includes, at the drive system control unit, determining a force required to maintain the vehicle on an incline grade on which the vehicle is located. The method further includes, at the drive system control unit, communicating with a brake control unit of the vehicle to reduce or increase an amount of friction brake application applied to at least one of the first set of wheels or the second set of wheels of the vehicle based at least in part on the determined force to hold the vehicle on the grade of incline. The method further comprises the following steps: at the drive system control unit, input from an operator control for stopping the vehicle while traveling on a grade is received, wherein the force is determined in response to the received input. The method further comprises the following steps: at the drive system control unit, while the electrical deceleration is decreasing, communicating with the friction brake control unit to increase the amount of friction brake application based at least in part on the determined force to stop the vehicle and stop the vehicle on the grade.

In another embodiment, a method of controlling a vehicle includes, at a drive system control unit of the vehicle, controlling an electric drive system associated with at least a first set of wheels of the vehicle to selectively provide electrical motive power to the at least first set of wheels to propel the vehicle and electrically slow the vehicle to slow the vehicle. The method further includes, at the drive system control unit, determining a force required to maintain the vehicle on an incline grade on which the vehicle is located. The method further includes, at the drive system control unit, communicating with a brake control unit of the vehicle to reduce or increase an amount of friction brake application applied to at least one of the first set of wheels or the second set of wheels of the vehicle based at least in part on the determined force to hold the vehicle on the grade of incline. The method further comprises, at the drive system control unit: receiving a first input from an operator control for stopping while the vehicle is moving on a grade (determining a force in response to the received input); communicating with the friction brake control unit to increase the amount of friction brake application based at least in part on the determined force to stop the vehicle and maintain the vehicle stopped on the grade; determining a torque level required to move the vehicle from a stop to an uphill grade; receiving a second input from the operator control for moving the vehicle up the grade; and in response to receiving receipt of the second input, communicating with the friction brake control unit to remove the friction brake application and simultaneously controlling the electric drive system to provide electric power according to the determined torque level for moving the vehicle from a stop to up the incline grade without significant vehicle rollback.

In another embodiment, a method of controlling a vehicle includes, at a drive system control unit of the vehicle, controlling an electric drive system associated with at least a first set of wheels of the vehicle to selectively provide electrical motive power to the at least first set of wheels to propel the vehicle and electrically slow the vehicle to slow the vehicle. The method further includes, at the drive system control unit, determining a force required to maintain the vehicle on an incline grade on which the vehicle is located. The method further includes, at the drive system control unit, communicating with a brake control unit of the vehicle to reduce or increase an amount of friction brake application applied to at least one of the first set of wheels or the second set of wheels of the vehicle based at least in part on the determined force to hold the vehicle on the grade of incline. The method further comprises, at the drive system control unit: receiving a first input from an operator control for stopping the vehicle while moving on a grade (determining a force in response to the received input); simultaneously with the electrical deceleration reduction, communicating with the friction brake control unit to increase the amount of friction brake application based at least in part on the determined force to stop the vehicle and maintain the vehicle stopped on the grade; determining a torque level required to move the vehicle from a stop to an uphill grade; receiving a second input from the operator control for moving the vehicle up the grade; and in response to receiving the second input, communicate with the friction brake control unit to remove the friction brake application and simultaneously control the electric drive system to provide electric power in accordance with the determined torque level for moving the vehicle up from a stop to an incline grade without significant vehicle rollback.

Thus, as should be appreciated, the control system of the present invention helps to address a number of issues related to vehicle launch and controlled vehicle stop on grade. In particular, embodiments of the control system may potentially mitigate unsafe vehicle movement during start-up on a grade, such as unintentional rollback on a grade when vehicle operation is initiated. Moreover, embodiments of the inventive subject matter may simplify the driving process for the operator. While typical vehicles require the operator to control three pedals for safe and smooth start and stop on grade, vehicles incorporating the control and braking system of the inventive subject matter require only a single pedal (or perhaps one brake pedal and one accelerator pedal) to be controlled by the operator due to the control system automating the start and stop process through communication and cooperation between the electric drive system and the friction brake system.

Embodiments of the inventive subject matter also function to avoid rough stops that potentially cause equipment damage, and facilitate controlled stopping of the vehicle by automatically controlling the transition from electric retarder braking to friction braking to maintain the vehicle on grade. Thus, a vehicle comprising the system is easier to drive and requires less expertise to operate. Moreover, easier handling of the vehicle translates into smoother vehicle operation and less wear on the components.

As noted above, embodiments of the present subject matter may be applicable to relatively large vehicles, such as haul trucks and other vehicles having a total vehicle operating weight of at least 250 metric tons. However, while the subject matter has been described with particular reference to OHVs and other large vehicles of this type, the subject matter is not intended to be so limited in this regard. In particular, it is contemplated that the inventive subject matter is equally applicable to electric vehicles in general, including, but not limited to, electric off-highway vehicles, automobiles, and the like.

As described above, the vehicle operator may be a human or an automatic controller. Thus, "operator controls" include both controls operable by a human and controls (e.g., control signals/inputs) associated with the control system/automation controller.

In one embodiment, a vehicle control system includes a controller configured to determine a non-zero upper limit for vehicle deceleration. The controller is configured to determine a non-zero upper limit to prevent the vehicle from rolling back along a grade on which the vehicle is traveling upward. A non-zero upper limit for deceleration is determined by the controller based on a load carried by the vehicle, a speed of the vehicle, and a grade of a current vehicle up-drive route. The controller is configured to monitor deceleration of the vehicle and automatically prevent the deceleration of the vehicle from exceeding a non-zero upper limit by controlling brakes and/or motors of the vehicle. The controller is further configured to activate the brake and/or supply current to a motor of the vehicle when the vehicle is moving up a grade at a non-zero speed to prevent the vehicle from rolling backwards.

Optionally, the controller is configured to activate the brake and/or supply current to the motor to prevent the vehicle from rolling backwards when the operator of the vehicle continues to activate the acceleration input device.

Optionally, the controller is configured to activate the brake and/or supply current to the motor after the operator releases the acceleration input device of the vehicle to prevent the vehicle from rolling backwards.

Optionally, the controller is configured to monitor deceleration of the vehicle as the vehicle moves in the selected direction of travel. The controller is further configured to automatically prevent deceleration of the vehicle beyond a non-zero upper limit by automatically controlling torque generated by the motor and/or activation of brakes of the vehicle when the vehicle is moving upward along a grade in a selected direction of travel.

Optionally, the controller is configured to monitor deceleration of the vehicle and automatically prevent the deceleration of the vehicle from exceeding a non-zero upper limit in response to upward travel of the vehicle along a grade of the route, the grade being a non-zero grade.

Optionally, the controller is configured to automatically prevent deceleration of the vehicle beyond a non-zero upper limit in response to the vehicle reaching a zero speed condition and before the vehicle begins to roll back down the grade.

Optionally, the controller is configured to automatically prevent deceleration of the vehicle beyond a non-zero upper limit by activating a brake of the vehicle. The controller may also be configured to subsequently release the brake and maintain the position of the vehicle on the grade by controlling the motor of the vehicle and not roll the vehicle backward down the grade.

Alternatively, a motor of the vehicle is powered by alternating current to propel the vehicle, and the controller may be configured to prevent the vehicle from rolling backwards by applying direct current to the motor.

Optionally, the controller is configured to prevent the vehicle from rolling backwards by applying direct current to the motor without applying brakes of the vehicle.

Optionally, the controller is configured to prevent the vehicle from rolling backwards by applying direct current to the motor and also applying brakes of the vehicle.

Optionally, the controller is configured to monitor torque generated by a motor of the vehicle and to release the brake in response to the torque generated by the motor exceeding a threshold torque required to prevent rollback of the vehicle.

Optionally, the controller is configured to determine the non-zero upper limit in response to a decrease in acceleration of the vehicle.

Optionally, the controller is configured to determine the non-zero upper limit such that the non-zero upper limit is decreased for heavier loads of the vehicle, lower speeds of the vehicle, or steeper grades of the route, and increased for lighter loads of the vehicle, faster speeds of the vehicle, or flatter grades of the route.

In one embodiment, a method includes determining a non-zero upper limit for deceleration of a vehicle to prevent the vehicle from rolling back along a grade on which the vehicle is traveling upward. A non-zero upper limit for deceleration is determined based on the load carried by the vehicle, the speed of the vehicle, and the grade of the current path traveled by the vehicle. The method further includes monitoring deceleration of the vehicle and automatically preventing the deceleration of the vehicle from exceeding a non-zero upper limit by controlling brakes and/or motors of the vehicle. When the vehicle is moving up a grade at a non-zero speed, the vehicle is prevented from slowing beyond a non-zero upper limit by activating the brake and/or supplying current to the motor of the vehicle to prevent the vehicle from rolling backwards.

Optionally, the deceleration of the vehicle is monitored as the vehicle moves in the selected direction of travel. Deceleration of the vehicle is automatically prevented from exceeding a non-zero upper limit by automatically controlling torque produced by the motor and/or activation of brakes of the vehicle when the vehicle is currently moving up a grade in a selected direction of travel.

Optionally, in response to the vehicle traveling up a grade of the route, the deceleration of the vehicle is monitored and automatically prevented from occurring beyond a non-zero upper limit, the grade being a non-zero grade.

Optionally, automatically preventing deceleration of the vehicle beyond a non-zero upper limit occurs in response to the vehicle reaching a zero speed condition and begins before the vehicle begins to roll back down the grade.

Optionally, the deceleration of the vehicle is automatically prevented from occurring beyond a non-zero upper limit by activating the brakes of the vehicle. The method may further include subsequently releasing the brake and maintaining the position of the vehicle on the grade by controlling a motor of the vehicle and not rolling the vehicle back down the grade.

Optionally, the vehicle is prevented from rolling backwards by applying a direct current to the motor, which is an alternating current motor.

Optionally, the controller is configured to identify a stop of acceleration of the vehicle in the selected direction of travel, and the controller is configured to automatically slow or stop movement of the vehicle in response to the rollback condition being identified, the operating speed of the motor exceeding a speed threshold, and the stop of vehicle acceleration being identified.

In one embodiment, a vehicle control system includes a controller configured to determine a lower speed limit of a vehicle. The controller is configured to determine a lower limit to prevent the vehicle from rolling back along a grade on which the vehicle is currently traveling upward. The lower limit is determined by the controller based on the load carried by the vehicle and the grade of the route currently being traveled by the vehicle. The controller is configured to monitor the speed of the vehicle and automatically prevent the vehicle speed from falling below a lower limit by activating the brakes of the vehicle. The controller is configured to activate the brake based on a speed of the vehicle and independent of an acceleration of the vehicle. The controller is further configured to activate a brake of the vehicle to prevent the vehicle from rolling backwards when the vehicle is moving up a grade at a non-zero speed.

Optionally, the controller is configured to monitor the speed of the vehicle after releasing the acceleration input device of the vehicle, and automatically prevent the speed of the vehicle from falling below the lower limit after releasing the acceleration input device.

Optionally, the controller is configured to monitor the speed of the vehicle as the operator continues to activate or depress the acceleration input device of the vehicle, and to automatically prevent the speed of the vehicle from falling below the lower limit as the operator continues to activate or depress the acceleration input device.

In one embodiment, a method comprises: receiving a throttle command indicative of an operator request to increase a throttle setting of the vehicle while a brake of the vehicle is engaged; increasing torque generated by one or more motors of the vehicle in response to receiving the throttle command; and releasing the brakes of the vehicle in response to one or more of the torque generated by the one or more motors reaching a maximum available torque, the torque generated by the one or more motors reaching a target release acceleration, or a predetermined non-zero duration over time.

In one embodiment, the method includes determining whether a brake of the vehicle is released when the vehicle is in a stopped state on a grade of the route; in response to determining that the brakes have been released, the vehicle is allowed to roll backward on a grade no greater than a specified non-zero threshold distance and/or the vehicle is rapidly accelerated using torque generated by one or more motors of the vehicle, and the vehicle is transitioned smoothly toward moving up the grade by adjusting torque generated by the one or more motors after the vehicle is allowed to roll backward on the grade and/or the vehicle is rapidly accelerated.

In one embodiment, a method includes repeatedly determining (when one or more brakes of a vehicle in a stationary position on a grade are engaged) during a blanking interval (blanking interval) whether an operator input to release the one or more brakes is received, releasing the one or more brakes of the vehicle in response to not receiving the operator input to release the one or more brakes during the blanking interval, and automatically generating torque using one or more motors of the vehicle to propel the vehicle upward along the grade.

It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the inventive subject matter without departing from its scope. While the dimensions and types of materials described herein are intended to define the parameters of the inventive subject matter, they are by no means limiting and are exemplary embodiments. Many other embodiments will be apparent to those of skill in the art upon reading the above description. As used herein, the terms "including" and "in white" are used as the plain english equivalents of the respective terms "including" and "wherein. Moreover, the terms "first," "second," "third," "upper," "lower," "bottom," "top," and the like are used merely as a distinction and are not intended to add numerical and positional requirements to these objects.

The foregoing written description uses examples to disclose several embodiments of the inventive subject matter, including the best mode, and also to enable one of ordinary skill in the art to practice embodiments of the inventive subject matter, including making and using any devices or systems and performing any incorporated methods.

As used herein, an element or step recited in the singular and proceeded with the word "a" or "an" should be understood as not excluding plural said elements or steps, unless such exclusion is explicitly recited. Furthermore, references to "one embodiment" of the present subject matter are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments "comprising," "including," or "having" an element or a plurality of elements having a particular property may include additional such elements not having that property.

Since certain changes may be made in the above-described systems and methods without departing from the spirit and scope of the inventive subject matter described herein, it is intended that all subject matter described above or shown in the accompanying drawings shall be interpreted merely as examples illustrating the inventive concept herein and shall not be construed as limiting the inventive subject matter.

Claims

1. A vehicle control system comprising:

a controller configured to determine a non-zero upper limit for vehicle deceleration, the controller configured to determine the non-zero upper limit to prevent the vehicle from rolling backwards along a slope on which the vehicle is currently traveling upwards, the controller determining the non-zero upper limit for deceleration based on a load carried by the vehicle, a speed of the vehicle, and a slope of a route on which the vehicle is currently traveling,

wherein the controller is configured to monitor the deceleration of the vehicle, the controller is configured to automatically prevent the deceleration of the vehicle from exceeding the non-zero upper limit by controlling brakes and/or motors of the vehicle, and

wherein the controller is configured to supply direct current to the motor of the vehicle to prevent the vehicle from rolling backwards when the vehicle is moving up the grade at a non-zero speed.

2. The vehicle control system of claim 1, wherein the controller is configured to supply direct current to the motor to prevent the vehicle from rolling backwards while an operator of the vehicle continues to activate an acceleration input of the vehicle or after the operator releases the acceleration input.

3. The vehicle control system according to claim 1,

the controller is configured to monitor the deceleration of the vehicle as the vehicle moves in a selected direction of travel,

the controller is further configured to automatically prevent the deceleration of the vehicle from exceeding the non-zero upper limit by automatically controlling torque produced by the motor and/or activation of the brakes of the vehicle when the vehicle is moving upward along the grade in the selected direction of travel.

4. The vehicle control system of claim 1, wherein the controller is configured to monitor the deceleration of the vehicle and automatically prevent the deceleration of the vehicle from exceeding the non-zero upper limit in response to the vehicle traveling up the grade of the route or in response to the vehicle reaching a zero speed condition and before the vehicle begins to roll down the grade backwards, the grade being a non-zero grade.

5. The vehicle control system of claim 1, wherein the controller is configured to automatically prevent the deceleration of the vehicle from exceeding the non-zero upper limit in response to the vehicle reaching a zero speed condition and before the vehicle begins to roll down the grade backwards.

6. The vehicle control system according to claim 1,

the controller is configured to automatically prevent the deceleration of the vehicle from exceeding the non-zero upper limit by activating the brake of the vehicle, and

the controller is configured to subsequently release the brake and maintain the position of the vehicle on the grade without rolling back the grade by controlling the motor of the vehicle.

7. The vehicle control system of claim 5, wherein the controller is configured to prevent the vehicle from rolling backwards by applying the direct current to the motor and not applying the brakes of the vehicle.

8. The vehicle control system of claim 5, wherein the controller is configured to prevent the vehicle from rolling backwards by applying the direct current to the motor and also applying the brake of the vehicle.

9. The vehicle control system of claim 1, wherein the controller is configured to monitor a torque generated by the motor of the vehicle and release the brake in response to the torque generated by the motor exceeding a threshold torque required to prevent the vehicle from rolling backwards.

10. The vehicle control system of claim 1, wherein the controller is configured to determine the non-zero upper limit in response to a decrease in acceleration of the vehicle.

11. The vehicle control system of claim 1, wherein the controller is configured to determine the non-zero upper limit,

such that the heavier the load of the vehicle, the lower the speed of the vehicle or the steeper the slope of the route, the smaller the non-zero upper limit, and

such that the lower the load of the vehicle, the higher the speed of the vehicle, or the slower the grade of the route, the greater the non-zero upper limit.

12. A method for controlling a vehicle, comprising:

determining a non-zero upper limit for deceleration of the vehicle to prevent the vehicle from rolling back along a current grade on which the vehicle is traveling, the non-zero upper limit for deceleration being determined based on a load carried by the vehicle, a speed of the vehicle, and a grade of a current route on which the vehicle is traveling;

monitoring deceleration of the vehicle; and

automatically preventing the deceleration of the vehicle from exceeding the non-zero upper limit by controlling a brake and/or a motor of the vehicle,

wherein the deceleration of the vehicle is prevented from exceeding the non-zero upper limit by supplying direct current to the motor of the vehicle when the vehicle is moving upward at a non-zero speed along the grade to prevent the vehicle from rolling backwards, the motor being an alternating current motor.

13. The method of claim 12, wherein,

monitoring the deceleration of the vehicle as the vehicle moves in a selected direction of travel, and

automatically preventing the deceleration of the vehicle from exceeding the non-zero upper limit by automatically controlling torque generated by the motor when the vehicle is moving upward along the grade in the selected direction of travel.

14. The method of claim 12, wherein the deceleration of the vehicle is monitored and automatically prevented from exceeding the non-zero upper limit in response to the vehicle traveling up the grade of the route, the grade being a non-zero grade.

15. The method of claim 12, wherein the deceleration of the vehicle is automatically prevented from exceeding the non-zero upper limit in response to the vehicle reaching a zero speed condition and before the vehicle begins to roll back along the grade.

16. A vehicle control system comprising:

a controller configured to determine a selected direction of travel of a vehicle, a direction of operation of a motor of the vehicle, and a speed of operation of the motor, the controller configured to identify a rollback state of the vehicle in response to the direction of operation of the motor of the vehicle being different from the selected direction of travel of the vehicle,

wherein the controller is further configured to automatically slow or stop movement of the vehicle by applying direct current to the motor, the motor being an alternating current motor, in response to identifying the rollback condition and the operating speed of the motor exceeding a specified non-zero speed threshold.

17. The vehicle control system according to claim 16,

the controller is configured to recognize an acceleration stop of the vehicle in the selected driving direction, and

the controller is configured to automatically slow or stop movement of the vehicle in response to identifying the rollback state, an operating speed of the ac motor exceeding the speed threshold, and identifying the acceleration stop of the vehicle.

18. A vehicle control system comprising:

a controller configured to determine a lower limit for a speed of a vehicle, the controller configured to determine the lower limit to prevent the vehicle from rolling back along a slope on which the vehicle is currently traveling upward, the controller determining the lower limit based on a load carried by the vehicle and a slope of a route on which the vehicle is currently traveling,

wherein the controller is configured to monitor the speed of the vehicle and automatically prevent the speed of the vehicle from falling below the lower limit by activating a brake of the vehicle, the controller is configured to activate the brake based on the speed of the vehicle and independent of an acceleration of the vehicle, and

wherein the controller is configured to apply direct current to an alternating current motor of the vehicle when the vehicle is moving up the grade at a non-zero speed to prevent the vehicle from rolling backwards.

19. The vehicle control system of claim 18, wherein the controller is configured to

Monitoring the speed of the vehicle after an acceleration input device of the vehicle is released, an

Automatically preventing the speed of the vehicle from falling below the lower limit upon release of the acceleration input device.

20. The vehicle control system of claim 18, wherein the controller is configured to monitor the speed of the vehicle as an operator continues to activate or depress an acceleration input device of the vehicle, and

automatically preventing the speed of the vehicle from falling below the lower limit while the operator continues to activate or depress the acceleration input device.